Australia paceman Pat Cummins acknowledged standing on the ball was a “mistake” but insisted he did not do it on purpose during the first day of the third Test against South Africa in Cape Town.

Match referee Andy Pycroft will surely examine footage of the incident as cricketers wear spikes that can damage the ball if stood on.

Former South Africa captain Graeme Smith joked on Fox Sports that Cummins, who starred on Thursday (local time) with four wickets, had “accidentally on purpose” stood on the ball.

Late in the day, Cummins snared 4-12 for Australia in an inspired spell that saw South Africa collapse from 2-220 to be 8-266 at stumps.

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Cummins said after play that it was “very unintentional” and that the on-field umpires had checked the ball following the incident.

“It was just a mistake … [I] looked straight back at him [umpire] and he just started to giggle … it was obviously very unintentional,” he said.

“There were no issues [once the ball was checked].”

Proteas opener Dean Elgar finished day one unbeaten on 121 while AB de Villiers again impressed in making 64.

But the day belonged to Australia given the flat nature of the Newlands pitch and the 400-plus total South Africa seemed headed for.

“We were in control for most of it,” de Villiers said afterwards.

“Unfortunately we lost our way and credit to them for sticking it out.”

The wicket of de Villiers started a period of Australian dominance, with Cummins making the key breakthrough when the South Africa star spooned a simple catch to David Warner at mid-off.

And Cummins quickly added the scalps of Faf du Plessis (five), Temba Bavuma (one) and Quinton de Kock (three) as he swung the course of the match.

The wickets kept coming, too, with bowlers Vernon Philander (eight) and Keshav Maharaj (three) falling just before stumps was called three overs early due to bad light.

“[This is] great bowling from Pat Cummins,” former Australia bowler Brendon Julian said on Fox Sports.

“Good pace, good bounce, good energy.”

Cummins finished the day with figures of 4-64 off 21 overs.

South Africa, who made two changes, bringing in Bavuma and the soon-to-be retired Morne Morkel, won the toss and elected to bat.

Opener Aiden Markram fell without scoring, though, edging the impressive Josh Hazlewood (2-37 off 18) to Steve Smith at second slip in the fourth over.

That brought Elgar and Hashim Amla (31) together and the pair were rarely troubled as the hosts moved to 1-75 at lunch.

Elgar made the most of his reprieve. Photo: Getty

Hazlewood came out breathing fire after the break and should have had both Amla and Elgar out in a sharp spell.

But he had to settle for just Amla – caught at fine leg from a surprise bouncer – when Nathan Lyon spilled a regulation chance after Elgar, on 53, hit one straight to him at point.

Lyon (0-39 off 19) completely misjudged his attempt, with the ball hitting him in the wrist, and Elgar made Australia pay by bringing up his 11th Test century.

Typically a dogged and dour opener, Elgar hit 16 fours and one six in just 178 deliveries to bring up his century and, pleasingly for the hosts, stayed at the crease for the entire day despite the late wickets.

Australia looked bereft of ideas early in the last session, with Elgar in good touch and de Villiers playing a typically stylish knock.

But just when another Test hundred seemed there for the taking, de Villiers was caught out by what he later described as “tennis ball bounce” and picked out Warner.

The wicket spurred Cummins on and he soon had both du Plessis and Bavuma caught by Smith at second slip before de Kock bottom-edged a pull shot to opposite number Tim Paine.

Philander has proved tough to dismiss in the series so far but Mitch Marsh (1-26 off seven) had him caught behind.

And there was still time for Mitchell Starc (1-81 off 21) to get a wicket on what was a tough day for him, when Maharaj picked out Cameron Bancroft in the covers.

Elgar will resume day two at the crease with Kagiso Rabada (six not out).